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<head>
  <meta charset="UTF-8">
  <title>JavaScript 数学</title>
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<body>
<h2>Math.sin()</h2>
<p>Math.sin(x) 返回角 x（以弧度计）的正弦（介于 -1 与 1 之间的值）。</p>


<p>以弧度计的角度 = (以度数计的角度) * PI / 180。</p>

<p id="demo"></p>

<script>
  document.getElementById("demo").innerHTML =
          "The sine value of 90 degrees is " + Math.sin(90 * Math.PI / 180);
</script>
</body>
</html>

<!--
运行结果：The sine value of 90 degrees is 1
-->